Many films and sheets, such as paper and plastic, are supplied in large heavy rolls having considerable inertia. If there is no auxiliary aiding means, the unwind operation must be started quite slowly, otherwise the film will be ruptured. Also, after normal operating speed of an unwind operation is underway, the high inertia of the storage roll tends to keep it turning and a fast stop is almost impossible without unwinding a large quantity of unwanted film. Many attempts have been made to control the movements of the storage roll by using complicated control means, either mechanical or electrical, but these means are expensive, difficult to maintain, and require precise adjustment of parts.
The present invention uses an array of simple components and avoids complication of construction. There are no control circuits as such and the mechanical units are simple, requiring a mechanic of only modest ability for service and maintenance. In the event of a component failure, replacement or repair can be made by replacing individual parts, easily and quickly.
One of the features of the present invention is the automatic nature of the aid components, helping to accelerate when starting up and braking when slowing to a stop.